1. Technical Field
The present invention relates to a test apparatus and a test method for testing a device under test such as an electronic device.
2. Related Art
Japanese Patent Application Publication No. 2006-317208 discloses a test apparatus that judges whether a device under test is defective based on a quiescent power supply current of the device under test. The test apparatus includes (i) a power supply that supplies the device under test with a driving power, (ii) a pattern generating section that supplies the device under test with a setting vector that sets a circuit of the device under test to a prescribed state, (iii) a power supply current measuring section that measures the quiescent power supply current supplied from the power supply to the device under test when the device under test is set to the prescribed state by the setting vector, and (iv) a judging section that acquires a temperature of the device under test using an internal temperature sensor and judges whether the device under test is defective based on the temperature of the device under test and the quiescent power supply current measured by the power supply current measuring section.
The defectiveness judgment based on the quiescent current IDDQ of the device under test uses the fact that a CMOSFET (Complementary Metal Oxide Semiconductor Field Effect Transistor) consumes almost no power when at rest, in other words, when the power supply current is not flowing. If a very small number of defective elements are present in a block under test, an excess current flows on the line supplying power to this block, so that a defect can be easily detected. Since recent advances in miniaturization of semiconductor devices have caused various types of defective modes, more complicated test patterns are used in function testing, and testing coverage is reduced. Taking this into account, a defectiveness judgment based on the IDDQ that can easily detect a wide range of defects is combined with other test methods to achieve an effective test method that can efficiently enhance test coverage.
However, miniaturization of the elements causes an internal leak current, even if the element is working normally. This makes it difficult to distinguish between a current flowing through a defective device under test and a current flowing through a non-defective device under test. Accordingly, a method for testing the IDDQ is sought that can distinguish between a normal current and an abnormal current to achieve a highly accurate defectiveness judgment, even if the miniaturization causes a leak current in the element.